Hot deformation of metals



United States Patent Office 2,706,850 Patented Apr. 26, 1955 HOT DEFORMATION F METALS Jacques Sejournet and Roger Emile Lambert, Paris, France, assignors to Comptoir Industriel dEtirage et Profilage de Metaux, Paris, France, a corporation of France No Drawing. Application February 27, 1951, Serial No. 213,049

Claims priority, application France March 10, 1950 1 Claim. (Cl. 29-423) This invention relates to the hot deformation of metals, particularly to extruding, forging, including drop forging and die forging, stamping, flattening, flanging, rolling, piercing, drawing and spinning.

An object of the invention is to facilitate the lubrication of the tools used in carrying out any hot deformation operation, thereby decreasing the wear on the tools and insuring the production of end products having excellent surface and other qualities.

In order to facilitate processes for hot deforming of metals, it is known to introduce a lubricant between the piece to be deformed (hereinafter referred to as the workpiece) and the tool used for the hot-working operation. Formerly, fatty substances of mineral, vegetable of animal origin were used for such purpose. However, under the influence of the heated workpiece these lubricants were partially burnt and were frequently thrown off from the tool under the action of the forces present before they could be effective. Additions of graphite or other substances in powdered form have been made to the fatty lubricants but their effectiveness at high temperatures is not all that could be desired.

More recently, various lubricants which have a sufficiently high viscosity at the hot deformation temperature have been proposed. For instance, it has been proposed to cover stamping dies with borax, to cover the billet to be forged and the forging dies with vitreous enamel in case of difficult forging operations, or to interpose a glass plate between the heated workpiece and the die of an extrusion press. But difiiculties are encountered in attempting to coat the workpiece uniformly or the tools with these lubricants since they are generally in the form of plates or powders, the application of which requires considerable care. Where it is desired to coat the tools, the lubricating substance must be in the form of a paste which is spread on the tool and left to dry. If it is desired to coat the heated workpiece with a lubricating powder, it can be sprinkled on the workpiece but it is diflicult to obtain a uniform distribution of the powder when employing such method.

These difficulties are overcome according to the present invention, which consists essentially in insuring most effective lubrication in the hot deformation of metals by using the lubricant in the form of a flexible sheet of glass fibers which is interposed between the tool and the heated workpiece which is to be deformed. The flexible sheet of glass fibers can be used to envelope the workpiece before placing it in the tool or to cover the surfaces of the tool which shape the workpiece.

The flexible sheet of glass fibers can be made in many ways, for instance, by weaving, felting, interlacing or intermingling of glass fibers either in the presence or absence of a substance acting as a binder for the fibers. It can be made up of granulated lubricant such as granulated glass enveloped by or interspersed in a flexible binder such as a felted fabric which itself may or may not be a lubricant or, if desired, the granulated lubricant can be enveloped by a flexible sheet of the same material as the granules if the material of the granules is of a nature to render it susceptible of being made into sheet form. One material which is particularly suited is a glass cloth or sheet made up of glass fibers assembled in such manner as to have a cohesion which permits their manipulation in the form of a single element.

The glass fibers constituting the glass cloth or sheet or fabric can be obtained by mechanical drawing of glass or by the action of a gaseous-fluid acting on a glass thread coming from a drawing apparatus or, if desired, by the action of centrifugal force on a mass of glass. The glass cloth or fabric can be made, for example, by depositing glass threads formed from liquid glass, on a pervious support on which they form a felt of fibers which are more or less tangled or interlaced, the cohesion of which can be, if desired, increased by the use of a binder. The cloth or fabric or sheet of glass fibers can also be obtained by continuous coiling of continuous fibers on a drum with addition of a binding material if desired.

When the metallic workpiece which is to be hot deformed is cylindrical, the glass cloth can be applied to the workpiece by spreading one or several flexible sheets of glass cloth on a table and rolling the heated workpiece on the glass cloth. The glass cloth adheres immediateh to the workpiece and covers it with a thin uniform layer which is quickly brought up to a temperature at which it assumes the desired viscosity for acting as a Lubricant in the hot deformation process. The preferred method of heating the workpiece prior to wrapping it with the glass cloth is by immersing the workpiece in a molten salt bath. This not only brings the workpiece up to proper temperature for extrusion but forms a coating of salt on the workpiece which aids the glass cloth in adhering to the workpiece.

If the workpiece is not cylindrical, for example, if it is of square cross section or is a flat disc, it can be heated and placed on a sheet of glass cloth and the glass cloth can be folded around the workpiece to cover those parts which it is desired to lubricate in a hot deformation operation. The glass cloth in contact with the heated workpiece assumes quickly a viscosity which facilitates the lubrication of the tool in the hot deformation operation. The workpiece covered with the glass cloth according to the present invention can then be hot deformed by usual processes. The employment of the glass cloth results in a considerable reduction in the friction between the workpiece and the tool and this reduction in friction lowers the forces required in performing the hot deformation operation and reduces wearing of the tools and tearing of the product being deformed.

When the tool is covered with one or several thicknesses of glass cloth, the cloth under the influence of the heat of the workpiece to be deformed and the forces involved in the hot deformation operation assumes the shape of the tool and rapidly attains the desired viscosity.

As previously pointed out, the present invention is applicable in general to the hot deformation of metal. However, some non-limiting examples will be given for purposes of illustration.

Example J.Extruding solid shapes tainer there is a die and at the other end there is a punch by means'of which the deforming force is transmitted to the billet to extrude it through the die. In order to reduce friction a lubricant is placed between the billet and the container.

According to the present invention, the heated billet is rolled on a sheet of glass cloth before its introduction into the container. This insures rapid and uniform lubrication during the extrusion operation.

Example 2.-Exzruding tubes In producing steel tubes by a method in which an extrusion press is employed, a heated previously pierced billet is mounted on a mandrel and the tube is extruded between a die and the mandrel. In one method now employed the friction between the billet and the mandrel is reduced by placing a glass sleeve between the billet and the mandrel.

According to the present invention, several turns of flexible glass cloth are wound around the mandrel before the hollow cylindrical steel billet is placed on the mandrel and thereafter the billet and mandrel are placed in the container of the extrusion press and the tube is extruded through the die. The application of the glass cloth to the mandrel is easy to accomplish, provides uniform lubrication between the billet and the mandrel, and results in tubes hav1ng more regular inner surfaces than those obtained by prior known processes. 7

Example 3.Ht drawing of tubes Example 4.-Stamping or die forging A die provided with a recess is covered with a sheet of glass cloth, a heated piece of steel is then placed on the glass cloth covering the die and the heated piece of steel is covered with another sheet of glass cloth and a stamping or forging operation is carried out in the usual manner.

The stamping or forging operation proceeds very easily and the metal fills the recess in the die more rapidly and more completely and the wear of the die is much less than in prior known stamping or forging operations.

The invention is not limited to the preferred embodiment but may be otherwise embodied or practiced within the scope of the following claim.

What We claim is:

A method of deforming metals, which comprises interposing between a metal workpiece and a deforming tool, a flexible sheet of intermingled fibers of glass-like material and deforming the workpiece at a temperature such as to cause the glass-like material to melt at least partially but remain viscous.

References ited in the file of this patent UNITED STATES PATENTS 2,074,224 Johnson May 13, 1935 2,430,083 Sherman Nov. 4, 1947 2,469,473 Orozco et a1 May 10, 1949 2,538,917 Sejournet et al Jan. 23, 1951 FOREIGN PATENTS 607,285 Great Britain Aug. 27, 1948 OTHER REFERENCES American Machinist, May 15, 1950, page 112. 

1. A METHOD OF DEFORMING METALS, WHICH COMPRISES INTERPOSING BETWEEN A METAL WORKPIECE AND A DEFORMING TOOL, A FLEXIBLE SHEET OF INTERMINGLED FIBERS OF GLASS-LIKE MATERIAL AND DEFORMING THE WORKPIECE AT A TEMPERATURE SUCH AS TO CAUSE THE GLASS-LIKE MATERIAL TO MELT AT LEASE PARTTIALLY BUT REMAIN VISCOUS. 